Surely you can buy one approaching end of life? They don't fly the engines or airframe forever.
Also, this sentence a couple of paragraphs down:
> Though buying a 747 plane and blowing it up may have been more efficient, Christopher Nolan later seems to insinuate that it may not have been the cheaper option
seems to muddle the waters somewhat.
More seriously, is the metal on an old airframe of high quality? I'd wonder whether the accumulated decades of wear and weathering might make it hard to recycle for anything like another airplane. But this isn't my field, so I'm just guessing.
I could easily see them spending more on that than the scrap value of the plane. But presumably the stunt coordination itself is also expensive.
Movie "explosions" don't usually actually explode things, that would be dangerous to the crew. They just make pretty flames, and use air cannons to send stuff flying in controlled ways.